The present invention generally relates to a light energy converting cell and, more particularly, to a Schottky barrier solar cell, and to a method of fabricating it.
In recent years, cells, using metal-semiconductor (Schottky) barriers in place of p/n junctions, to convert light energy to electrical energy, have been investigated. Such cells are often referred to as Schottky-barrier-type cells. Most of the investigation has been directed to converting sunlight to electrical energy. Therefore, hereinafter for explanatory purposes in describing the prior art as well as the invention, the cell will be referred to as the Schottky barrier solar cell. Some of the advantages of a Schottky barrier solar cell are its simplicity, higher current output and improved radiation resistance.
Typically, such a solar cell includes a substrate, consisting of a single crystal gallium arsenide (GaAs) wafer. The bottom side of the GaAs wafer is metallized to form one terminal of the cell, while a thin semiconductor layer of GaAs is then vapor-epitaxially grown on top of the GaAs wafer. A very thin layer of metal is deposited on top of the vapor-epitaxially grown GaAs layer. A grid electrode is then deposited on the metal layer to serve as the other cell terminal. Often, an antireflection coating is applied to the exposed surface of the metal layer. To provide sufficient strength for the cell, the single crystal GaAs wafer, which serves as the cell substrate, has to be relatively thick (on the order of about 10 mils. The cost of such a wafer is quite high, thereby greatly increasing the cell cost. Reducing cell cost would greatly increase the potential use of Schottky barrier solar cells.